The present invention concerns equipment such as skis and snowboards which, during the execution of a turn, necessarily incur a degree of sideslip. Of interest to someone attempting to perfect their skiing technique is the amount of sideslip or skidding of the skis during a turn. Good skiers execute turns with minimal sideslip to avoid loss of speed, while intentional sideslipping or skidding is an accepted way of killing speed prior to stopping.
In the prior art, U.S. Pat. No. 3,505,878 discloses a speed and distance indicator pivotally carried on the tail of a ski and equipped with a pair of wheels for contact with the snow surface. U.S. Pat. No. 3,888,500 shows a ski boot actuated device for indicating the displacement of boot during execution of a turn. U.S. Pat. No. 4,864,860, issued to the present inventor, discloses an electrical generator assembly swingably carried on the tail of a snow ski. The generator can pivot, in response to side imparted loads during a turn, about an upright axis. U.S. Pat. No. 4,088,019 discloses a device for sensing true leeway of a vessel in relationship to a vessel centerline. A servomechanism maintains a vane of the device vertical.